U.S. patent application number 11/974802 was filed with the patent office on 2009-08-20 for highly efficient supersonic laminar flow wing.
This patent application is currently assigned to Aerion Corporation. Invention is credited to James D. Chase, Michael Henderson, Peter Sturdza.
Application Number | 20090206206 11/974802 |
Document ID | / |
Family ID | 39766629 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090206206 |
Kind Code |
A1 |
Chase; James D. ; et
al. |
August 20, 2009 |
Highly efficient supersonic laminar flow wing
Abstract
Improved supersonic laminar flow wing structure, on a supersonic
aircraft, having one or more of the following: strake extending
forwardly of the wing inboard extent, raked wing tip, reversed
fillet at strake or fuselage junction, inboard leading edge flap
extending over less than about 15% of the inboard wing panel span,
hybrid plain-split flap having a lower surface portion deflectable
downwardly relative to plain flap extent.
Inventors: |
Chase; James D.; (Reno,
NV) ; Henderson; Michael; (Piedmont, SC) ;
Sturdza; Peter; (Atherton, CA) |
Correspondence
Address: |
WILLIAM W. HAEFLIGER
201 S. LAKE AVE, SUITE 512
PASADENA
CA
91101
US
|
Assignee: |
Aerion Corporation
|
Family ID: |
39766629 |
Appl. No.: |
11/974802 |
Filed: |
October 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60852929 |
Oct 18, 2006 |
|
|
|
Current U.S.
Class: |
244/199.4 ;
244/198; 244/214; 244/217 |
Current CPC
Class: |
B64C 30/00 20130101;
Y02T 50/30 20130101; B64C 7/00 20130101; B64C 9/18 20130101; B64C
9/24 20130101; B64C 3/10 20130101; Y02T 50/10 20130101 |
Class at
Publication: |
244/199.4 ;
244/198; 244/214; 244/217 |
International
Class: |
B64C 21/00 20060101
B64C021/00; B64C 23/06 20060101 B64C023/06; B64C 3/50 20060101
B64C003/50 |
Claims
1. Improved supersonic laminar flow wing structure, on a supersonic
aircraft, having one or more of the following: a) strake extending
forwardly of the wing inboard extent, b) raked wing tip, c)
reversed fillet at strake or fuselage junction, d) inboard leading
edge flap extending over less than about 15% of the inboard wing
panel span, e) hybrid plain-split flap associated with the wind and
having a lower surface portion deflectable downwardly relative to
plain flap extent.
2. The combination of claim 1 wherein the strake has a leading edge
swept more than the Mach angle at maximum supersonic speed of the
aircraft.
3. The combination of claim 2 wherein the strake has i) a blunt
leading edge, ii) camber.
4. The combination of claim 1 wherein the raked wing tip has i) a
blunt leading edge, ii) more sweep than the Mach angle at maximum
cruise speed of the supersonic aircraft.
5. The combination of claim 1 wherein said reverse fillet has a
convex leading edge profile at said junctions.
6. The combination of claim 1 wherein said inboard leading edge
flap is positioned for deployment from one or both of the
following: i) a cavity in the strake or fuselage, ii) about a pivot
axis associated with the strake or fuselage.
7. The combination of claim 1 wherein said hybrid plain-split flap
is a trailing edge flap and has one of the following: i) a split
flap hinge line co-located with the plain flap hinge line, ii) a
split flap hinge line located aft of the plain flap hinge line.
8. The combination of claim 7 wherein the plain flap is downwardly
deflected by a first angle and the split flap is downwardly
deflected by a second angle, wherein the second exceeds the
first.
9. The combination of claim 4 wherein said reverse fillet has a
convex leading edge profile of said junctions.
10. The combination of claim 8 wherein said inboard leading edge
flap is positioned for deployment from one of the following: i) a
well in the strake or fuselage, ii) about a pivot axis associated
with the strake or fuselage.
11. The combination of claim 9 wherein said hybrid plain-split flap
is a trailing edge flap and has one of the following: i) a split
flap hinge line co-located with the plain flap hinge line, ii) a
split flap hinge line located aft of the plain flap hinge line.
Description
[0001] This application claims priority from U.S. provisional
application, Ser. No. 60/852,929, filed Oct. 18, 2006.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to efficient, supersonic,
laminar flow aircraft wing configurations. More specifically it
concerns improvements in the following configuration areas:
[0003] a) strake,
[0004] b) raked wing tip,
[0005] c) reversed fillet wing-strake junction,
[0006] d) inboard leading edge flap,
[0007] e) hybrid plain-split flap.
[0008] Certain prior Richard Tracy patents disclose a laminar flow
wing for efficient supersonic flight (U.S. Pat. Nos. 5,322,242,
5,518,204, 5,897,076 and 6,149,101). Recent developments have led
to five areas of improvement, principally benefiting low speed
characteristics of aircraft using the wing. The wing described in
the prior Tracy patents has a sharp, modified biconvex airfoil,
with less than about 30 degrees leading edge sweep in order to
maintain an attached shock at supersonic cruise conditions, and
thickness-chord ratio (t/c) of about 2% or less as a span-wise
average over the majority of the wing. The latter excludes a zone
near the inboard end, which may be thicker, up to about 4% t/c in
combination with fuselage area ruling.
[0009] There are several unique characteristics of the supersonic
laminar flow wing which pose challenges, especially in low speed
flight. These include its sharp leading edge which causes a
separation "bubble" at almost any angle of attack in subsonic
flight, its extremely thin airfoil which imposes a structural
weight penalty as aspect ratio is increased, and the un-swept
leading edge which limits the effectiveness of "area ruling" the
wing-body for minimizing supersonic wave drag. These (and other
characteristics) are unique to the supersonic laminar wing and are
substantially mitigated by the herein claimed improvements, acting
individually or together, in combination with this type of
wing.
SUMMARY OF THE INVENTION
[0010] Two of such improvements utilize features which have been
used in aircraft design, but not in conjunction with the supersonic
laminar flow wing under consideration. These are a "strake" and a
"raked" tip. Three additional features are unique to the supersonic
laminar wing. These are a "reverse fillet", a deployable flap at
the inboard end of the leading edge, and a hybrid plain-split flap
system. All five are described below.
Strake
[0011] The strake is a highly swept portion of the wing between the
fuselage and the inboard end of the un-swept main wing panel. The
strake's leading edge is preferably swept forward of the wing to an
intersection with the fuselage, and its trailing edge may be a
continuation of the outer wing trailing edge, or may be swept
further aft to a fuselage intersection. The leading edge is
preferably swept more than the Mach angle at the maximum supersonic
cruise speed in order to have a "subsonic leading edge". This
condition assures a detached shock wave and permits the leading
edge of the strake to be somewhat blunt and cambered for less
supersonic drag, and enhanced low speed lift capability of the
wing, or its maximum "lift coefficient".
[0012] The strake performs several functions in addition to
increasing maximum lift in the present application, while favorably
affecting supersonic cruise performance. These are as follows: 1.
Increases the span of the wing for improved lift efficiency with
less structural weight penalty, 2. Improves the longitudinal
distribution of fuselage and wing cross sectional area for lower
supersonic wave drag, 3. Provides additional volume for fuel in the
forward part of the aircraft, 4. Creates a vortex at moderate and
high angles of attack in subsonic flight which tends to keep the
flow attached over the upper inboard wing surface for better lift
and engine inlet flow quality, 5. Helps maintain laminar flow over
the inboard portion of the wing, and 6. Provides a structural hard
point for landing gear mounting and space for gear retraction.
Raked Tip
[0013] The "raked tip" is a highly swept lateral edge, or wing tip,
of the wing, which may have either a sharp or slightly blunted edge
as long as it has more sweep than the Mach angle at the maximum
cruise speed. The tip adds two important attributes to the type of
wing under consideration.
[0014] It adds to the span and thus the aspect ratio without as
much associated drag-causing wetted area and structural bending as
would a conventional rounded or blunt tip. More importantly, in low
speed flight it generates a "rolled up" vortex at up to moderate
angles of attack, which remains attached to the upper surface of
the wing tip. The attached tip vortex delays the growth of the
leading edge separation bubble and resultant loss of lift over the
outer portion of the wing. This, in turn, increases the maximum
lift of the wing and prevents, or delays, the inboard movement of
the tip vortex associated with loss of outer wing lift. The result
is a lower downwash derivative with angle of attack over the
horizontal tail, providing greater longitudinal stability and
reduced tendency to pitch up.
Reversed Fillet
[0015] The wing-strake (or wing fuselage) junction on most aircraft
is subject to detail treatment in form of a "fillet" or concave
surface blending smoothly with the wing and fuselage surfaces. This
fillet is generally associated with a concave curve in plan view
between the leading edge and the fuselage.
[0016] For the laminar flow wing the necessity of avoiding
excessive boundary layer cross-flow can be very difficult at the
wing leading edge to strake (or fuselage) junction because the
large up-wash at the junction causes Mach waves (pressure
disturbances) and locally higher chord-wise pressure gradients on
the wing surface. These effects can cause locally critical levels
of boundary layer cross-flows, which can in turn destabilize the
laminar flow over a substantial portion of the inner wing,
resulting in a turbulent boundary layer and higher skin friction
drag. However by making the leading edge profile convex at the
strake (or fuselage) junction, so as to eliminate, or even slightly
reverse, the sweep locally at the strake junction, cross-flows can
be reduced to below critical levels and transition to turbulence
substantially reduced.
Inboard Leading Edge Flap
[0017] A second consequence of the strong up-wash near the leading
edge junction with the strake (or fuselage), in combination with
the sharp leading edge is a premature growth of the leading edge
separation "bubble" leading to early loss of lift over the inboard
portion of the wing. This results in a delay of maximum lift to
high angles of attack. Full span leading edge flaps can delay the
formation and growth of the leading edge "bubble", but such devices
are mechanically awkward with the very thin, sharp leading edge of
the laminar wing, and are difficult, if not impossible, to
implement without any surface gap or disturbance which would
preclude laminar flow.
[0018] A more practical solution is a leading edge flap extending
over only the inboard 15%, or so, of the wing panel span outboard
of the strake or fuselage. Such a device, for example a Kruger flap
extending forward of the leading edge, has been shown by
proprietary tests to be very effective on this type of wing. It can
be deployed from the strake (or fuselage) with a minimum of leading
edge mechanization by various means, such as moving the flap
laterally from a cavity in the strake (or fuselage), or by swinging
it about a vertical pivot axis from a stowed position in the strake
(or fuselage).
Hybrid Plain-Split Flap
[0019] The thin laminar flow wing is not suited to multi-element
slotted flaps, slotted fowler flaps, or even "zap" flaps, because
of lack of interior space and the undesirability of external hinges
and tracks. For these reasons a plain hinged trailing edge flap is
the most practical approach. However the lift increment which can
be generated, especially with the sharp leading edge wing, is
limited by separation of the flap upper surface.
[0020] A simple split flap (lower surface only deflected) has
slightly higher maximum lift capability than a plain flap, but at a
penalty in drag. In any case, a split flap would not be consistent
with the need for small amounts of flap deflection for efficient
subsonic and transonic cruise, which is required for most
applications of the laminar supersonic wing.
[0021] For this type of wing a hybrid combination of split and
plain flap offers unique advantages. The hybrid split flap is
configured such that a portion of the flap lower surface can
deflect down relative to the plain flap. The split flap hinge line
can be co-located with the plain flap hinge, or preferably aft of
it, near mid chord of the plain flap. When deflected, the split
flap delays separation on the upper surface of the plain flap by
lowering the wake pressure and reducing the adverse pressure
gradient at the flap upper surface trailing edge. Since the outer
portions of the plain flap are the most vulnerable to such
separation, the split flap also mitigates tip stall and the
increased downwash that would result as described in connection
with the raked tip above.
DRAWING DESCRIPTION
[0022] FIG. 1 herein shows a supersonic aircraft wing, strake, flap
and leading edge flap;
[0023] FIG. 2 is a plan view of a supersonic wing showing locations
of the FIG. 3 flap structure; and
[0024] FIG. 3 is a section view of the wing airfoil of a supersonic
laminar flow wing, showing trailing edge and inboard leading edge
flap structures.
DETAILED DESCRIPTION
[0025] In the drawings, the preferred supersonic aircraft 10 has a
fuselage 11, thin, laminar flow wing 12 including left and right
wing sections 12a and 12b, jet engines 13 closely proximate
opposite sides of the fuselage, and tail 14.
[0026] The strake is shown at 15, as a highly swept portion of the
wing between the fuselage 11 and the inboard end 16 of the low
sweep main wing panel. Other strake characteristics are referred to
above.
[0027] The raked tip of each wing section is shown at 17, and has
characteristics as referred to above.
[0028] Reversed fillet configuration, for each strake-fuselage
junction leading edge, is indicated at 19, and has characteristics
as referred to above.
[0029] The inboard leading edge flap is shown, for each wing
section, at 18, and has characteristics as referred to above, and
may have association with cavities in the fuselage or strake.
[0030] Hybrid plain-split flap, for each wing section, is provided
at 21, and has characteristics as referred to above, and includes
plain flap 21a and split flap 21b. Suitable actuators for the flaps
are indicated schematically at 35, and may have association
cavities in the fuselage or strake. The hinge line for 21b is at
21c. In FIG. 3, the hinge line for the split flap may be co-located
at or aft of 21c, with respect to plain flap 21a.
[0031] In FIG. 3, plain flap 21a is downwardly deflected by a first
angle relative to a plane substantially coincident with the plane
of wind and split flap 21b is downwardly deflected by a second
angle relative to said plane, where the second angle exceeds the
first angle.
[0032] Similar relationships exist where the hinge line for the
split flap is co-located at 21c.
* * * * *